Biochemical and morphological techniques will be combined in an effort to characterize in subcellular and molecular terms the mechanisms whereby arterial smooth muscle cells become overloaded with lipid and converted to foam cells in atheromatous lesions. The work will focus on the chemical composition of the lipid deposits, both in deoplets and in lysosomes, and on the enzymes and carriers involved in lipid processing. The time course of the events will be analyzed, both in a chronic and in an acute model. The experiments will be carried out on aortic cells from rabbits fed on diets variously enriched in cholesterol, on de-endothelialized arteries, and on human specimens obtained at surgery or at autopsy.